Heat-resistant stainless steel castings （SCH materials as specified in JIS G 5122） are commonly used for fire grates that transport waste inside waste incinerators. However, in chlorine gas environments generated from waste containing large amounts of plastic, the protective Cr₂O₃ scale proves insufficient, potentially leading to premature failure. In this study, it was demonstrated that ferritic heat-resistant cast steel with an increased Si content, compared to conventional heat-resistant cast steel, exhibits improved corrosion resistance due to the formation of a protective Si-based scale. Furthermore, it was confirmed that increasing the carbon content significantly enhances corrosion resistance.

The occupancy sites of Mg in the corrosion products formed on the steel substrate at cut-edge of the Zn‒11Al‒3Mg （mass％） coated steel was investigated by XAFS analysis at the initial corrosion stage. At the cut-edge, corrosion products containing Zn and Mg were formed in the early stages of corrosion. The XRD and XAFS analyses revealed that the corrosion products at the cut-edge of the Zn‒11Al‒3Mg coated steel were Mg-containing Zn₅（OH）₈Cl₂・H₂O. Based on the first-principles calculations, Mg in Zn₅（OH）₈Cl₂・H₂O was more likely to substitute two types of the crystallographic sites of Zn rather than intercalate between the ZnO₆ and ZnO₃Cl layers. Therefore, Zn₅（OH）₈Cl₂・H₂O, with two types of the crystallographic sites of Zn partially substituted by Mg, was thought to be formed at the cut-edge of the steel substrate of Zn‒11Al‒3Mg coated steel at the initial corrosion stage.